Arming and firing mechanism



Hmleys rig@ Feb. 13, 196s Filed oct'. 22, 1965 United States Patent O 3,368,488 ARMING AND FIRING MECHANISM Virgil H. Johnson and John L. Hill, Champaign, Ill., as-

signors to The Magnavox Company, Fort Wayne, Ind., a corporation of Delaware Filed Oct. 22, 1965. Ser. No. 501,522 16 Claims. (Cl. 102-81) ABSTRACT F THE DISCLOSURE An arming and firing mechanism which is responsive to conditions of hydrastatic pressure includes a sensitivity operable trigger which can function only after the device is at a predetermined hydrostatic pressure and at such pressure, the device is then prepared for firing by means of a pressure-responsive device which moves, enabling access of a striker to a detonator which impa-cts against the detonator when a triggering mechanism is operated. The triggerin-g mechanism is a mechanical operation which swiftly biases the pin against the charge.

This invention relates generally to explosives, and more particularly to an arming and tiring mechanism capable of enabling or causing the firing of an explosive charge in response to certain operating conditions, such as environmental pressure, for example.

Although it is a common endeavor to provide arming mechanisms which are safe to handle, but reliably armed at the desired time, certain operating conditions often cause great difficulty with conventional apparatus. This is particularly true where the device is to be deployed in deep-water, high-pressure environments.

It is therefore a general object of the present invention to provide an improved arming and firing mechanism.

A further object is to provide a mechanism adapted to operate under adverse environmental conditions, and particularly deep-water, high-pressure, ocean environments.

A further object is to provide a mechanism which can be safely assembled and handled after assembly, and which becomes armed only when intended.

A further object is to provide a completely selfcontained sealed unit, which will not admit moisture or become contaminated during storage and handling, and yet performs its function by tiring through a hole in an external wall.

A further object is to provide a unit which is readily mountable to a variety of types and configurations of explosive devices.

A further object is to provide a device which is readily adaptable to either arming alone or both arming and tiring, in response to environmental pressure above a selected level.

A further object is to provide a device which is automatically re-saiing upon removal of the selected arming pressure, before firing. .Y

Described briefly, a typical embodiment of the present invention includes a closed and sealed housing assembly havin-g a hammer pin therein which is driven through a wall of the housing upon tiring, to actuate the explosive device with which the mechanism is employed. The mechanism includes a cylinder in the housing which receives an arming piston assembly containing a detonator and normally biased to a safe position by a spring. An aperture is provided in the housing to admit water to one side of the piston, which is sealed to the cylinder in the housing to move the piston toward armed position as the environmental pressure overcomes the arming piston spring. The piston can thereby be moved to a position of alignment of the detonator therein with the hammer pin and with 3,368,488 Patented Feb. 13, 1968 ICC a striker guide and locking sleeve which is normally positioned to lock the striker and held in that position by the arming piston.

When the piston is moved to armed position by the environmental pressure, the striker guide and locking tube is unblocked, to enable the striker to strike the detonator, and the detonator, being fired thereby drives the hammer pin through a thin wall section of the mechanism to lire the device with which the mechanism is used.

A special high pressure sealing arrangement is provided on the piston which, although it avoids interference with proper pressure response of the piston, prevents admission of water to the interior of the housing in spite of extremely high hydrostatic pressures encountered at great ocean depths.

The full nature of the invention will be understood from the accompanying drawings and the following description and claims:

FIG. 1 is a schematic view of a self-embedment anchor device in which the arming and tiring mechanism of the present invention can be employed.

FIG. 2 is an enlarged section through a typical embodiment of the arming and tiring mechanism of the present invention, the section being taken on a plane containing the axis of the mechanism, and showing it attached to an explosive assembly used in the anchor system.

FIG. 3 is a section like that of FIG. 2, but showing another embodiment of the mechanism mounted to the lower end of a different type of explosive device.

FIG. 4 is an enlarged fragment of FIG. 2 illustrating the novel sealing arrangement according to the present invention.

Referring now to the drawings in detail, FIG. 1 shows a self-embedment anchor package which includes a canister 11 having a rounded lower end 12 with an insert 13 in the center of the lower end. This package includes a cable pack 14 consisting of many turns of anchor cable concentric with the axis 16 of the package. As the package is deployed in water, anchor cable =pays out through the hollow upper end 17, the upper end of the cable being connected to a oat or some other device to be anchored.

An anchor probe 18 is located on the axis and has liukes 19 fold-able against the body of the anchor for containment in the package but which can be opened by any suitable means when the anchor 18 enters the ocean bottom. To cause the anchor to enter the ocean bottom, it is provided with a shaft received in a gun barrel 21 and the arming and tiring mechanism 22 of the present invention is used to fire the :propellent charge in the :barrel 21 which drives the anchor and uke assembly out the plug 13 in the bottom of the canister and into the bottom of the ocean, for example.

This is one example of an application wherein the arming and tiring mechanism of the present invention is useful. Once the anchor 18 is driven into the ocean bottom and the ilukes 19 expand, the anchor, which is connected to the canister by another cable serves to hold whatever is connected to the cable 14, anchored to the bottom.

Referring now to FIG. 2, the upper end of the gun barrel is shown at 21 and a propellent cartridge assembly 23, shown fragmentarily, is disposed therein and includes a percussion primer 24 at the upper end and a main .propellent charge 26, which, when ignited, drives the anchor shaft 18 down and out of the barrel to drive the anchor out of the canister. The arming and firing mechanism of the present invention, in the em-bodiment illustrated in FIG. 2, includes a housing 27 threadedly received at 28 in the canister 11 and having a cover 29 affixed to the upper end thereof by a plurality of screws such as screw 31. A seal ring 32 is received in a circular groove in the lower face of the cover and abuttingly engages and seals against 3 the upper face of the housing 27 to exclude water from the interior regardless of the depth to which the unit is submerged. A similar seal ring 33 is provided in a circular groove in the lower face of the housing and is compressed against the upper `face 34 of the priopellent cartridge assembly so as to exclude water from the upper end of the propellent cartridge assembly, regardless of depth.

A hammer is provided near the lower end of the housing and includes a cylindrical hammer body 36 and a hammer pin 37, the body being received in a guiding bore in the housing and the pin received in a smaller bore below the guiding bore and terminating a short distance above the lower face 38 of the housing. Accordingly there is provided a thin section `39 of the housing material homogenous with the rest of the material of the housing and which is disposed immediately under the rounded lower end of the hammer pin and isolatng the hammer pin and the interior of the housing from the percussion primer 24. This section also isolates the hammer pin and the interior of the housing from the environment.

The upper end of the hammer body 36, and the bore in which it is received, abuts the cylindrical surface 41 of an arming piston 42 which is slidingly received in a stepped bore in the housing, this bore having a rst portion 43 of smaller diameter than the portion 44 and separated therefrom by a step face 46 which serves as a high pressure seal seat, as will be shown.

An arming piston spring 47 between the bottom 48 of the bore portion 43 and inner end 49 of the arming piston, forces the piston against a piston cover 51 retained in the housing by snap ring 52 received in a groove in the housing.

The piston 42 is provided with two annular sealing ring grooves 53 in which low-friction bore sealing rings are received. These rings exclude water `from the interior of the housing, lbut do not prevent the pressure drop across the piston from moving the piston inward toward the piston bore end 48 as the pressure differential increases, Which occurs during descent of the unit in water. Of course the pressure differential must exceed the initial spring force on the piston for any movement of the piston to occur at all.

The piston is -pr'ovided with a transverse stepped bore therein, the upper portion 54 of which serves as a locking tube receiver, as will be described, the intermediate portion of which serves to mount the detonator S6, and the lower portion `57 of which provides a passage for communication of energy from the detonator to the upper end of the hammer body when the ypiston has moved from the safe position shown in FIG. 2 to the armed position.

A striker 58 is disposed in the central bore 59 of a cylinder `61 having a pair of additional bores 62 equally spaced from the central axis 16 and extending from the lower end 63 to the upper end y64. The striker is down- Wardly lbiased by the spring 66 received in the striker bore 59 but is prevented from moving downwardly by two striker detent balls 167, each oif which is received in a transverse aperture in the lower end portion 68 of the cylinder 61. These balls are large enough that when they are prevented from moving out beyond the outer cylindrical surface of the portion 68, they project into the striker guide bore between the striker and the arming piston. To keep the balls confined in the position shown in FIG. 2, a striker housing 69 is provided with an in- Wardly projecting ange 71 at the lower end thereof having an inner cylindrical wall 72 receiving the portion 68 and closing enough of the apertures to prevent the balls frommoving out of position. Immediately below this flange, a lball release cavity 73 is provided in the housing and its purpose will soon be described.

Having described most of the parts illustrated in the embodiment of FIG. 2, the remainder of the apparatus may be best understood by proceeding with the operation.

Operation As suggested above, the illustrated device is intended to become armed when the environmental pressure reaches a certain level. In order to preclude any arming at all, regardless of pressure, a safety pin 74 is received through the cover 29, housing 27, and piston 42, and serves to prevent the piston from moving inward in its bores. A pull ring 76 is provided at the upper end of the safety pin, to facilitate manual pulling thereof, when intended, or other means could be employed such as by connecting the pull ring through a wire or cable to a float so as to pull the ring and pin after the device has descended a certain distance in the water.

After the safety pin has been pulled, the only thing preventing movement of the piston inward is the spring 47, and the load thereon is selected so that inward movement of the piston does not begin until the pressure differential across the piston is that existing at a desired arming bias depth in the water. Further increase of pressure will move the piston toward the bore end 48 until abutment of the piston face 77 with the bore face 46. Thereupon the lower end of the striker tube portion 68 of the cylinder 61 is able to move into the socket 54 which is now centered on the axis 16. The tube does not, however, automatically descend into the bore, because the cylinder is biased upwardly by the inertial release bias spring 78, whose lower end rests on the ange 71, urges the cylinder up against the lower face of the cover. However, with the transverse bores of the piston thus aligned on the axis 16, the detonator is aligned with the hammer pin and all that is required to release the striker is for something to overcome the spring 78.

In the particular application of the invention, it is desired to re the anchor when the canister strikes the ocean bottom. Since the descent of the canister is suddenly slowed or stopped when it strikes the bottom, the inertia of the cylinder 61 tends to keep it descending against the bias of the spring 78, so that the lower end of the striker tube can enter the socket 54 whereupon the locking balls are cammed out through the apertures into the cavity 73 by the tapered surface on lthe striker itself and the striker spring drives the striker into the detonator. When the detonator tires, it drives the hammer pin through the thin section thereunder and into the percussion primer which then explodes the main propellent 26 to drive the anchor out of the canister and into the ocean bottom material.

An important feature of the present invention is the fact that the structure enables relatively free movement of the piston when desired in response to increased hydrostatic pressures, for arming, but nevertheless prevents leakage into the interior even when subjected to extremely high hydrostatic pressures. For this purpose, an O-ring seal 79 is received in a groove adjacent the face 77 on the piston, the groove being concave at 81 so that the ring is normally properly seated thereon without engagement with the cylindrical bore wall 44. The O-ring projects slightly beyond the face 77 toward the seat 46 so that, when the pressure across the piston has moved the piston near the armed position, with the face 77 and seat 46 near each other, the O-ring will begin to be compressed against the seat 46. Further increase of Apressure and corresponding movement of the piston `to the armed position increases the sealing pressure of the O-ring against the seat and the abutment of the faces 77 and 46 prevents extrusion of the O-ring out of place.

Another feature of the .construction of the present invention is the fact that, if the arming and tiring mechanism is again brought up to less than the arming bias depth, before firing, the spring 47 will again ,return it to the safe position. The decrease of hydrostatic pressure will have allowed the high pressure seal 79 to return to its condition of disengagement from the bore, and the low pressure seal ring 53 will continue to exclude water from the interior of the housing.

Another feature of this embodiment of the invention is the fact that even if the device illustrated in FIG. 2 became armed and was fired accidently while it was separate and apart from the explosive device with which it is to be used, no harm will be done to any person either handling the device r in the vicinity. The reason for this is the fact that although the hammer body bore 82 in the housing is deeper than the hammer body itself, to permit the tiring pin to penetrate the thin section 39 and extend therefrom to tire the primer 24, there remains a circular abutment 83 in the housing under the hammer body and well above -the lower face 38 of the housing so that ample housing material is provided under the hammer body to stop the hammer and prevent it from being ejected entirely from the housing. Consequently, only the firing pin end portion pierces and protrudes from the housing even when the device illustrated in FIG. 2 is fired.

With the construction of the present invention, in the safe position, the detonator is out of line with the striker and cannot be tired by the striker even if the striker were released. Also the detonator is out of line with the harnmer and the percussion primer would not be tired by the hammer pin even if the detonator were to lire. Accordingly this arming and firing mechanism is quite safe for handling and storage.

Another feature is the fact that because the lower bore portion 57 in the piston is of smaller diameter than the hammer body 36, the hammer is fixed in the position illustrated both when the mechanism is safe and when it is armed, until it is tired.

The hammer is driven by a detonator requiring only a small energy input to fire it. This makes possible the use of an inertia mass such as that of the cylinder 61 to enable tiring the detonator upon ocean bottom impact. Yet it permits the percussion primer 24 to be an insensitive explosive element which can only be fired by a sharp blow of considerable energy upon its at face. Since it is quite insensitive to firing, it is safe to be in contact with the propellent of the propellent cartridge assembly, at all time. Because of the energy requirement to re the percussion primer, it is impractical to design a spring loaded, out of line tiring mechanism of suicient output energy but sensitive enough to reliably tire inertially on impact with a soft ocean bottom material. The present invention however makes it possible to use the sensitive inertially iired detonator which, in turn, liberates sufiicient energy to force the hammer pin through the thin wall section at the bottom of the housing and strike the percussion primer with a concentrated blow of comparatively high energy, sufficient to iire it.

The described arming and tiring mechanism is a` sealed assembly against moisture and contamination during storage and handling but is able to vperform its percussion primer firing function by tiring through a hole in the external wall. It has a sensitive, low-G firing capability making it capable of tiring reliably when used with a device which impacts soft ocean bottom materials. Being a complete self-contained inertially red unit, which can be tired on soft ocean bottom impact, there is no need for external linkages or high pressure'dynamic seals, "or high pressure loaded moving parts, for operation.

FIG. 3 shows another embodiment ofv the invention which omits some ofthe structure described above, and

which incorporates variations in other structure. This embodiment is. not inertially red but is fired immediately upon arming. This embodiment might be used for tiring a high explosive charge 86 at a predetermined depth. In this embodiment, the explosive device 87 has a main explosive charge 86 which can be detonated by an explosive booster charge 88 which can be fired by the explosive lead charge 89 disposed in the arming and tiring mechanism housing 91 in place of the hammer pin of FIG. 2. Also, instead of the safety pin 74 of FIG. 2, a shear safety pin 92 is provided in thehousing 91 and extends therethrough and through the piston 42 in the same manner as in- FIG. 2. However, this pin is designed to hold the arming piston in the safe position until the pin is Vsheared by the hydrostatic load on the arming piston. The pressure which will shear the pin, is suicient to move the arming piston inwardly to alignment of the detonator 56 and the transverse bores of the piston with the striker 58 and the explosive lead charge. In this embodiment, the striker tube is spring loaded by the striker release Spring 93,'and the striker locking balls are confined by the loading sleeve 94. As soon as the piston moves to the armed position, the spring 93 can drive the upper end of the tube into the socket 54, and as soon as the apertures 96 become uncovered as the striker tube rises, the tapered surface 97 of the striker forces the balls out into the ball release cavity 98 and the striker is driven into the sensitive detonator by the striker spring 66. The firing of the sensitive detonator is effective to tire the less sensitive explosive lead charge, which releases suiiicient energy to iire the explosive booster charge 88. The lead charge 89 can be designed to blast a hole through the thin section 99 of the housing under the booster charge to fire the booster charge.

Regardless of the installation, the casing or housing to which the arming and tiring mechanism is threadedly received can be provided with radial apertures as at 100 in FIG. 3 and which communicate with the circumferential groove 101 in the threads of the arming and tiring mechanism housing so that regardless of the rotational position of the housing with respect to the case, water is always able to enter the groove 101 and pass through the aperture 102 in the cover plate 51 to push against the end of the arming piston. Also it should be apparent that the 'embodiment shown in FIG. 2 can be used with a variety vof devices other than the anchor tiring vgun shown in FIGS. 1 and 2 and could be used to fire high explosive charges on impact. Similarly, the embodiment of FIG. 3 can have a variety of applications and can include employment with an anchor tiring gun to lire the anchor at a predetermined depth, without the necessity of there iirst being an impact.

While the invention has been disclosed and described in some detail in the drawings and foregoing description, they are to be considered as illustrative and not restrictive in character, as other modiiications may readily suggest themselves to persons skilled in this art and within the broad scope of the invention, reference being had to the appended claims.

The invention claimed is:

1. In an arming and tiring mechanism, the combination comprising:

a housing;

`energy output means in said housing;

a detonator; mechanical firing means effecting trigger operation of said detonator;

arming means having a portion in alignment with said ring means normally preventing tiring of said detonator by forming an obstacle to movement of said `tiring means which must be first displaced before firing and responsive to changing pressure to move said detonator into association with said energy output means and enable firing of said detonator at predetermined environmental conditions of said arming and tiring mechanism, yielding means opposing movement of said arming means into firing position, and thereby providing a shielding obstacle to be displaced before firing positioning said arming means in a normal position precluding iiring of said det'onator; said energy output means being responsive to firing of said detonator, when associated therewith, to provide a concentrated energy output from the mechanism and inertial means for actuating said mechanical tiring means to effect tiring when said arming means have been operated to a firing position responsive to changing pressure.

2. The combination of claim 1 wherein:

said housing includes a bore therein with an abutment at one end thereof;

said arming means includes a piston received in said bore, with rst low friction sealing means between the bore wall and piston wall to enable establishment of a pressure differential across said piston whereby said piston is drivable in said bore toward said abutment,

second sealing means are provided between said piston and said abutment and are sealingly compressed therebetween as said piston moves adjacent said abutment, said piston being drivable against said abutment by pressure differential across said piston, said second sealing means being mounted for entrapment by a surface of said piston abutting said abutment to prevent extrusion of said second sealing means in spite of extremely high pressure differentials across said piston.

3. The combination of claim 2 wherein:

said piston has a circular recess with a concave bottom extending to a flange face thereof facing said abutment;

said second sealing means is an O-ring received in said recess and normally spaced from said bore and projecting a small distance axially beyond said flange face and compressible against said abutment immediately prior to and during abutting engagement of said flange face radially inward of said ring with said abutment.

4. The combination of claim 1 wherein:

said housing has a bore therein;

said arming means includes a piston linearly movable in said bore between a safe position and an armed position and sealed to said bore to enable establishment of a pressure differential across said piston;

a safety pin extends in said piston and housing and normally prevents movement of said piston from said safe position in said housing.

5. The combination of claim 4 wherein said pin has an end projecting beyond the end of said housing with means thereon enabling withdrawal of said pin from said housing to enable said piston to move in said housing.

6. The combination of claim 4 wherein said pin is constructed for shearing by said piston when the pressure differential across said piston has risen to a predetermined level.

7. In an arming and firing mechanism, the combination comprising:

a housing;

energy output means in said housing;

a detonator;

arming means normally in a safe position preventing tiring of said detonator, and responsive to operating conditions to move said detonator into association with said energy output means and enable firing of said detonator at predetermined environmental conditions of said arming and ring mechanism; mechanical firing means including an inertial tiring member responsive to impact of said arming and ring mechanism to effect trigger operation of said detonator;

said housing having a thin wall section adjacent said energy output means and isolating said energy output means .from the environment outside said housme;

said energy output means being responsive to tiring of .said detonator, when associated therewith, to deform said thin wall section and provide a concentrated energy output from said housing.

8. The combination of claim 7 wherein said energy output means is a hammer having a body and la pin, said pin being drivable through said thin section, but said housing having an abutment therein adjacent said thin section and abuttingly engageable by said body after rupture of said section by said pin, to prevent ejection of said hammer from said housing.

9. The combination of claim 7 wherein said energy output means is a hammer, said hammer being immovably confined by said arming means and said housing when said arming means are in said safe position.

10. The combination of claim 7 wherein said energy output means is an explosive charge rable by said detonator.

11. In an arming and tiring mechanism, the combination comprising:

a housing;

energy output means in said housing;

a striker in said housing biased for movement in a first predetermined path;

a detonator;

arming means normally holding said detonator out of the path of said striker and responsive to operating conditions to move said arming means and thereby move said detonator into the path of said striker, said detonator being then associated with said energy output means; triggering means for effecting forcible operation of said striker which is translated at high speed under predetermined operating conditions, said triggering means including mechanical firing means having an inertial firing member responsive to impact of said arming means to effect trigger operation of said detonator;

and striker locking means normally limi.ing movement of said striker, said arming means controlling said locking means and responsive to changing operating conditions to enable said locking means to release said striker,

and driving means operable, when release of said striker is caused, to drive said striker into said detonator and lire it, said detonator thereupon activating said energy output means associated therewith.

12. The combination of claim 11 wherein:

said arming means is a slider, spring biased to .safe

position;

said striker locking means include tube means with an aperture in a wall thereof, said tube means having an open end abutting said slider and confined by said slider when said slider is in .safe position;

said striker is guidingly and slidingly received in said tube means;

said tube means has the outer end of said aperture thereof normally closed by a wall member in said housing adjacent an outer wall surface of said tube means;

said striker locking means include a detent ball received in said aperture and restrained by said wall member to project into said tube means between said slider and a portion of said striker to prevent said striker from being moved toward said slider by said driving means;

said driving means is a spring located in said tube means and compressed between said striker and a closed end of said tube means.

13. The combination of claim 12 wherein:

said slider has a socket therein and said detonator is aligned with said socket, said socket being sized to permit release of said tube means and movement of the open end portion of said tube means into said socket, when said slider has moved said detonator into the path of said striker;

.said wall member covering said aperture being of limited length in the direction of movement of said tube means whereby said aperture is opened when said tube means moves into said socket, to permit said detent ball to move out of said cylinder and release said striker.

14. The combination of claim 13 wherein:

said tube means is spring biased toward said slider and is thereby moved into said socket immediately upon align-ment of said socket with said tube means.

15. The combination of claim 13 wherein:

said tube means is normally biased away from said slider, and is operable by inertia upon an impact, to move into lsaid socket after alignment of said socket with said tube means.

16. The combination of `claim 13 wherein:

sealing means are provided between a portion of said slider and a portion of said housing, said housing and slider and sealing means being arranged so as to be the only portion of the combination'exposed to the exterior environment whereby said energy output means, said striker, said detonator, said striker locking means, and said driving means are isolated from the environment existing outside said housing, regardless of the pressure thereon.

References Cited UNITED 7/1907 3/1937 5/1945 9/1951 l/l962 7/1962 10/1966 10/1966 1l/l966 STATES PATENTS Meigs et al 10'2-79 Morpeth et al 102-79 Adelman 102-70 Bowersett et al 102-7 Domingos et al 102-7 Stresau et al 102-70 X Tower et al 102-7 Vass et al. 102-76 X Kent 102-70 BENJAMIN A. BORCHELT, Primary Examiner.

G. H. GLANZMAN, Assistant Examiner. 

